38 Stanley K. Sessions and John E. Wiley 



Morescalchi 1975). Kezer et al. (1965) presented karyological evidence 

 that supports this view. Hecht and Edwards (1976) reviewed the system- 

 atic data for these groups of salamanders and concluded that morpho- 

 logical information is not sufficient to resolve this problem, and that 

 more biochemical and karyological studies are needed. 



One of the most thorough treatments to date of the genus Necturus 

 is that of Hecht (1958), who recognized four species on the bases of 

 external morphology, ontogeny, and geographic distribution: Necturus 

 beyeri Viosca, Necturus lewisi (Brimley), Necturus maculosus (Rafi- 

 nesque), and Necturus punctatus (Gibbes). He also tentatively recog- 

 nized a subspecies of N beyeri, N b. alabamensis Viosca, but described 

 it as "one of the most distinct forms in the genus" (Hecht 1958:17), and 

 seemed somewhat ambivalent as to its taxonomic status. Subsequently 

 Brode (1970) revised the genus, mainly on osteological grounds, recog- 

 nizing two species, TV. maculosus and N punctatus, and six subspecies: 

 TV. m. maculosus, N m. lewisi, N m. walkeri, N p. punctatus, N p. 

 alabamensis, and TV. p. beyeri. The present systematic status of this 

 group of salamanders is one of uncertainty and disagreement, mostly 

 because there are so few distinguishing morphological features between 

 the various forms. Nevertheless, most recent workers recognize five 

 species — TV. alabamensis, N beyeri, N lewisi, N maculosus, and TV. 

 punctatus — as well as several subspecies of TV. maculosus (Brame 1967; 

 Gorham 1974; Conant 1975). 



All species of Necturus, with the exception of TV. maculosus, are 

 distributed along the Coastal Plain of southeastern United States, from 

 southeastern Virginia to eastern Texas (Fig. 1). Necturus maculosus is 

 by far the most widely distributed species, with a range extending fan- 

 like from an apex in Louisiana and broadening northward to southeast- 

 ern Manitoba in the west and southeastern Quebec in the east, essen- 

 tially encompassing the entire Mississippi River drainage system. The 

 combined ranges of these species result in a more-or-less continuous 

 distribution of Necturus over most of eastern North America, inter- 

 rupted in the east by the Appalachian Mountains which form a wedge 

 separating the two coastal species, TV. lewisi and TV. punctatus, from 

 inland populations of TV. maculosus. According to Brode (1970), partial 

 sympatry and morphological intergraduation may occur between TV. 

 punctatus and TV. alabamensis, and between the latter form and TV. 

 beyeri. Necturus lewisi and TV. punctatus, however, are the only species 

 definitely known to occur in sympatry, and are morphologically the 

 most distinct of all Necturus species (Hecht 1958). 



Results of a recent electrophoretic analysis by Ashton et al. (1980) 

 suggest that at least three species, TV. maculosus, TV. lewisi, and TV. punc- 

 tatus, are distinct, long-isolated species. Only TV. maculosus has been 

 studied karyologically (Seto et al. 1964; Morescalchi 1975; Sessions 



